The invention relates to an organic electronic device. More particularly, the invention relates to metal compound-metal multilayer electrodes for organic electronic devices.
Efficient operation of organic electronic devices depends, among other factors, on efficient transport of electronic charges between an electrode and an adjacent medium. Organic electronic devices are used in several applications based on converting electricity into light and/or light into electricity. Exemplary electro-active devices, classified as either organic or inorganic devices, are well known in graphic display and imaging art. Electro-active devices have been produced in different shapes and sizes for many applications. Inorganic electro-active devices, however, typically suffer from a required high activation voltage and low brightness. On the other hand, organic electro-active devices, that have been developed more recently, offer the benefits of a lower activation voltage and higher brightness in addition to simple manufacture, and, thus, the promise of more widespread applications.
An organic electronic device is typically a thin film structure formed on a substrate such as glass or transparent plastic. An electro-active layer and optional adjacent organic semiconductor layers are sandwiched between a cathode and an anode. The organic semiconductor layers may be either hole (positive charge)-injecting or electron (negative charge)-injecting layers and also comprise organic materials. The electro-active organic layer may itself consist of multiple sublayers, each comprising a different electro-active organic material.
Reducing or eliminating barriers for charge mobility between electro-active organic layers and an electrode contributes greatly to enhancing the efficiency of an organic electronic device. Metals having low work functions, such as the alkali and alkaline-earth metals, are often used in a cathode material to promote electron injection. However, these metals are susceptible to degradation upon exposure to the environment. Therefore, devices using these metals as cathode materials require rigorous encapsulation. In addition, these metals can diffuse rapidly into an adjacent electro-active organic layer, leading to device performance decay.
It is hence desirable to provide for greater charge mobility between electro-active organic layers and the electrodes. Electro-luminescent and other electro-active devices, such as photovoltaic cells, can also benefit from a lower barrier for electron transport across the interface between an active layer and an adjacent cathode. Therefore, it is desirable to provide a cathode assembly and materials that efficiently allow charges to move more readily between an electrode and an adjacent layer.